The term polarizer is used to mean an optical device which transmits polarized light or components of natural light in given state of polarization, and blocks other components. In a narrower sense, therefore, a polarizer is a device for producing polarized light from natural light. "Natural light" means non-polarized light, i.e. white, colored monochromatic light. An "analyzer" is a polarizer used for analyzing the state of polarization of light.
The most widely-used polarizer is the sheet polarizer for producing linear-polarized light. These polarizers have the disadvantage that half the incident natural light is necessarily lost.
A polarizer which would deliver more than half of the incident light in the form of polarized light would be a considerable technical advance.
Unexpectedly, a polarizer has now been found which polarizes nearly all the incident natural light. It is based on frequency-selective reflection of cholesteric liquid crystals having a Grandjean structure in combination with a mirror used for reversing the direction of rotation of circular-polarized light.